System and method of atomizing reactive two-part fluids

ABSTRACT

An apparatus includes a first belt having an external surface, a second belt having an external surface positioned with the external surface opposite to the external surface of the first belt, with a region in which the first belt and the second belt come in contact, a first set of guide devices arranged inside the first belt, a second set of guide devices inside the second belt, a first material dispenser positioned to allow a first material to be dispensed on the external surface at least one of the first and second belts, a second material dispenser positioned to allow a second material to be dispensed on the external surface at least one of the first and second belts, and a power source to cause at least one of the guide devices in at least one of the first set and the second set of guide devices to cause at least one of the first and second belts to move to cause the external surfaces of the first and second belts contact and then diverge away from each other so that at least one of the first material and the second material forms filaments that break up as the belts continue to diverge. A method of generating a spray of reactive materials includes dispensing a first material onto at least one of a first belt and a second belt, the first belt and the second belt arranged on a first set of guide devices and a second set of guide devices, dispensing a second material onto at least one of the first belt and the second belt, mixing the first material and the second material by moving the first belt and the second belt through a region in which the first belt and the second belt come in contact with each other to form a mixture, and causing the first belt and the second belt to diverge from each other forming filaments that break into a spray of droplets.

TECHNICAL FIELD

This disclosure relates to atomizing viscous fluids, more particularlyto atomizing two-part fluids using a filament extension atomizer.

BACKGROUND

Spraying or otherwise making a mist from highly viscous fluids presentsseveral challenges. Viscous fluids do not flow easily and any process ofbreaking them up into particles has to overcome the inherentcohesiveness of the fluid.

One successful solution to this issue lies in filament extensionatomizers (FEA) developed by PARC. In the most common of theseatomizers, the system introduces the fluid to one or both surfaces of apair of counter-rotating rollers or other diverging surfaces. As thesurfaces come into contact, or near contact in a region called the nip,the fluid attaches to both surfaces. As the surfaces rotate away fromeach other, the fluid stretches between them, forming filaments. As thesurfaces continue to move, the filaments burst into droplets.

Generally, the use of these atomizers involve a non-reactive fluid. Theterm ‘reactive” fluids generally involve at least two differentcomponents like an epoxy resin and a hardener, referred to here as areactive system. Many challenges of trying to spray these fluids exist.To effectively react, the two fluids need to undergo sufficient mixingso the cross-linking agent can react more uniformly, and therefore forma more complete, uniform cross-linked material. Pre-mixing in a chamber,such as a reservoir or pump body, will not work well. The two fluidswill react, resulting in clogging of the fluid dispenser as thecross-linking will cause blockages in the dispenser. The cross-linkingmay also make the dispenser difficult to clean as the fluids may stickto the chamber in which they mixed, even to the point of formingdifficult to remove solids. Rapidly reacting fluids may become notsprayable at all.

SUMMARY

According to aspects illustrated here, there is provided an apparatusincludes a first belt having an external surface, a second belt havingan external surface positioned with the external surface opposite to theexternal surface of the first belt, with a region in which the firstbelt and the second belt come in contact, a first set of guide devicesarranged inside the first belt, a second set of guide devices inside thesecond belt, a first material dispenser positioned to allow a firstmaterial to be dispensed on the external surface at least one of thefirst and second belts, a second material dispenser positioned to allowa second material to be dispensed on the external surface at least oneof the first and second belts, and a power source to cause at least oneof the guide devices in at least one of the first set and the second setof guide devices to cause at least one of the first and second belts tomove to cause the external surfaces of the first and second beltscontact and then diverge away from each other so that at least one ofthe first material and the second material forms filaments that break upas the belts continue to diverge.

According to aspects illustrated here, there is provided a method ofgenerating a spray of reactive materials includes dispensing a firstmaterial onto at least one of a first belt and a second belt, the firstbelt and the second belt arranged on a first set of guide devices and asecond set of guide devices, dispensing a second material onto at leastone of the first belt and the second belt, mixing the first material andthe second material by moving the first belt and the second belt througha region in which the first belt and the second belt come in contactwith each other to form a mixture, and causing the first belt and thesecond belt to diverge from each other forming filaments that break intoa spray of droplets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of a system to atomize reactive, two-partfluids.

FIG. 2 shows an alternative arrangement of guide devices in a system toatomize reactive, two-part fluids.

FIG. 3 shows an alternative arrangement of guide devices in a system toatomize reactive, two-part fluids.

FIG. 4 shows an embodiment of an operational system to atomize reactive,two-part fluids.

FIG. 5 shows an embodiment of a pair of belts having different textures.

FIGS. 6-7 show alternative embodiments of a system to atomize reactive,two-part fluids.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Generating sprays or mists from highly viscous materials presentsseveral problems, mostly due to the ‘thickness,’ or resistance to flowof the material. The particles of the materials tend to have internalfriction between layers of the fluid that flow at different rates,making them ‘sticky’ and hard to separate from other particles of thematerial. The terms “highly viscous” or “high viscosity” mean aviscosity of over 1 mPa-s (milliPascal-second).

The filament extension atomizer (FEA) technology developed at PARCemerged as a solution to this problem. FEA enables spraying of highlyviscous formulations. Thin, low viscosity fluids, with or without apropellant, can be sprayed using pump or trigger sprayers. These methodsdo not work with higher viscosity fluids, but the FEA has had success inspraying these liquids.

Generally, FEA systems have diverging surfaces, such as a pair ofcounter rotating rollers. The two surfaces come into contact and thenmove away from each other. Typically, a fluid is applied to one or bothof the surfaces. The surfaces move towards each other and come intocontact, or near contact, then diverge from each other. During contact,the fluid sticks to the surfaces, and then as them move away from eachother, the fluid forms filaments that stretch between the surfaces untilthe strain causes the filament to break up into droplets and form aspray.

The discussion here involves using an FEA system for reactive, fluidsmaterials or systems. As used here, the term “reactive” means that afirst material, when it comes in contact with a second material, causesa reaction in which the first material causes the second material tocross-link or otherwise change their composition. As used here, the term“cross-link” includes cross-linking, curing, or hardening. Materialsthat change their composition can include foaming materials that reactto form a gas phase that creates voids in the material, materials thatchemically react with each other, materials that cause properties suchas pH to change, or materials that combine to form other alloys orcopolymers. One should note that the first and second materials,individually, may comprise more than one material, such as across-linkable material and a buffering agent.

Cross-linkable materials comprise those materials that can form chemicalbonds between different chains of atoms of a polymer or other complexmolecule. Examples include but are not limited to, a material containingone or more of epoxy resin, silicone resin, or cross-linkable polymers.Examples of materials that can cause other materials to cross-link,referred to here as cross-linking agents, include epoxy hardeners,silicone hardeners, and polymer cross-linkers, such as boric acid.

In a FEA system using two counter rotating rollers the contact areabetween the rollers is small. In a reactive system, this means that areactive material spends little time in contact with the other fluidbefore it is atomized. Since a mixing of these two fluids can take time,the small contact area reduces the ability to increase the contact timewithout slowing the roller speeds down to a point where spray quality oroutput is decreased. Furthermore it can be difficult to increase thecontact area and time between the two rollers by increasing the size ofthe rollers since increasing the size of the rollers only has a smallimpact on the contact area and greatly increases the size of the overallsystem.

In order to address concerns with using two roller to create filaments,two belts are used to create both a contact area and the divergingsurface for the creation of FEA spray. Using belts as the divergingsurfaces allows a system to be created with a smaller footprint, butwith a large contact area to encourage mixing of the two fluids to forma reactive solution. This allows compact FEA systems with a long contactarea, but still capable of running at high surface speeds to createfilaments that breakup and meet output demands from an application.

In the case of using belts as the diverging surfaces, the rollers orother guide devices take on a different role than being the divergingsurfaces themselves. This separates the guide devices from being thediverging surfaces. As used here, the term “guide device” means anydevice that moves, or just directs, the belts. The guide devices maycause the belts to move, such as powered rollers, including thosemounted on a shaft, connected to motors that cause the rollers to spin.Examples include rollers, and rollers with sprockets. The belt could bea timing belt. These then in turn cause the belt to move. Other types ofguide devices may take the form of more passive devices, such as rollersthat only move because the belt causes the rollers to spin, or even assimple as a pin or other structure that merely directs the belt in aparticular direction.

Guide devices can take a wide range of shapes and configurations. Theycan be smooth rollers that are mounted on a shaft. The shaft isconfigured to a bearing system that allows the roller and shaft assemblyto freely rotate. Guide devices such as rollers can also be configuredso that there is a bearing between the roller and a fixed shaft, this iscommonly known as an idler. In addition to smooth rollers, the guidedevice can be a toothed gear or other substantially circular shape withfeatures to contain and guide a belt. In addition to substantiallycircular roller-like shapes, rigid shapes that a belt is allowed tofreely glide over or past can be used to create geometries not otherwiserealizable with circular features. These shapes may include triangular,rectangular, square, etc. Stationary, or passive, guide devices caninclude features that help constrain motion of the belt in a directionother than the linear velocity of the belt. This can include guiderails, pins, or grooves. Additionally, the guides can be eccentricallymounted around an axis of rotation so that as the belt moves through andaround the device the belt moves against the opposing belt.

FIG. 1 shows an embodiment of a system 10 to generate a spray from areactive system. The system comprises an FEA components of two sets ofguide devices, in this case rollers, a first set 12 and a second set 14.Each set of guide devices reside inside a belt, like the set of guidedevices 12 that reside inside the belt 16, and the set of guide devices14 that reside inside belt 18. The two dispensers 26 and 28 dispensetheir materials on at least one of the sets of guide devices in the areaof 20. Each dispenser could dispense its material onto separate belts,both onto one belt, or both onto both belts. However the materials aredispensed, they enter the region between the two belts where they comeinto contact. In one embodiment, the dispenser may comprise a slot-diedispenser and a doctor blade, such as 27 and 29.

These materials then mix in that region. The guide devices are arrangedto form areas of high pressure such as 20, and areas of low pressuresuch as 22. These alternating regions assist with the mixing of thematerials to form a mixture. As the belts move, as shown in the figurethey would both move left to right, and then diverge. Their divergencecauses the mixture to form filaments 30, that will eventually break upinto droplets such as 32. This is discussed in one more issued patents,such as U.S. Pat. No. 9,962,673, “Methods and Systems for CreatingAerosols,” issued May 8, 2018, and its related cases.

Using belts in place of a single pair of counter rotating rollers allowsfor adjustments that would not otherwise be possible. The systemcontroller could move the guide devices to extend the length of theregion in which the surfaces are in contact. In addition, the controllermay control the speed, or pressure, of the belts to control the amountof time the materials mix. Generally, the controller 24 manages theoperation of the dispensers 26 and 28, and the guide devices that movethe belts. The controller may control any number of guide devices fromone to all. Controlling one of the guide devices may cause one of thebelts to move, which, because of the friction between the belts maycause the other belt to move. A power source, such as a battery, ACpower from the grid, etc., provides the impetus to the guide device ordevices the move the belts, possibly by a motor or other drive.

Other configurations of the belts and guide devices are also possible,and may take up less space. FIG. 2 show the FEA component comprising thetwo sets of rollers in a different orientation. In this orientation thefluids would be applied at 34 and the filaments and spray would occur at36. This embodiment may include supplemental guide devices such as 38.The supplemental guide devices may create more or longer regions of highpressure. One should note that “high” pressure and “low” pressure arerelative each other.

FIG. 3 shows an alternative embodiment of the FEA components, in whichthe guide devices for each belt are offset from each other. As usedhere, the term “offset” means that the rollers alternate compared to theopposing guide device in opposite set. In FIG. 3 , the first guidedevice 40 is offset laterally from the first guide device 44 in theopposite set. The configuration of guide devices as in FIGS. 1 and 2 maybe referred to here as a “linear” configuration, where the guide devicesused for each belt are in a line of close proximity to each other.Similarly, guide device 42 is offset from its counterpart guide device46, and guide device 52 is offset from guide device 54.

In the embodiment of FIGS. 1-3 , the rollers may be fixed into theposition shown at the configuration of the system. Alternatively, thefirst configuration of FIG. 3 , may include actuators attached to atleast some of the guide devices, such as 58 and 56. The actuators couldthen move the guide devices near each other to the second configurationshown in FIG. 3 . Alternatively, the second configuration shown in FIG.3 could be the way the guide devices are configured. The regions of highpressure such as 48 and low pressure such as 50 are arranged differentlythan other embodiments.

FIG. 4 shows a drawing of an operable system. In this system, the beltsare timing belts. A timing belt generally differs from a regular belt inthat it has teeth, and the teeth may match with the rollers such as 64.This allows for precise control of the motion of the belt with regard totime. The belts could both move at the same speed, or one could move ata faster rate than the other to enhance mixing.

Other method of enhancing mixing may involve other differences in thebelts, in addition to moving them at different speeds. As shown in FIG.5 , one belt 70 may have a smoother surface than the belt 72, which mayhave a rough or textured surface. In addition, the two belts may be heldat different voltages if the two components have different dielectricconstants.

Other variations of guide devices, belts and their shapes are of coursepossible. FIGS. 6 and 7 show alternative configurations of the system.In FIG. 6 , the upper belt 80 has a drive motor 82, connected to atleast one of the two guide devices 84 and 86 that may comprise rollers.Other guide devices such as 90 may comprise passive or active devicesthat cause the first belt to come into contact with the second belt andthen diverge as shown by the arrow. A tensioner 88 may maintain theappropriate the appropriate tension. The dispensers in this embodimentcomprise slot-die coaters 92, 110 and doctor blades 94 and 110. Thesecond belt 96 has a drive motor 98, connected to one or more of therollers 100 and 102. The other guide devices such as 106, and atensioner 104.

This embodiment includes a harvesting air flow. While not shown inprevious embodiments, any of the other embodiments may includeharvesting air flows. The harvesting air flows flow in the directionsshown by arrows 110 and 112. The harvesting air flows direct thedroplets in a predetermined direction. While shown flowing in aparticular direction as in FIG. 6 , the harvesting air flow could bedirected wherever desired.

FIG. 7 shows an alternative embodiment in which a first belt 120 and asecond belt 132 move to come into a region in which they are in extendedcontact. The guide devices 122 and 124, guide the first belt 120. Anactuator 130 move in the direction of the arrow shown to cause the beltto move towards the other belt 132. The other belt 132 has guide devices134 and 136, as well as an actuator 142. The dispensers 126 and 140 havecorresponding doctor blades 128 and 138, if that type of dispenser isbeing used. The harvesting air flow travels in and out of the plane ofthe page as shown by arrow 144.

In this manner, using belts instead rollers provides better mixing, andmore opportunities to control the rate and length of the mixing region.This overcomes the issues with mixing materials in a reactive system,while also overcoming issues with viscosity.

All features disclosed in the specification, including the claims,abstract, and drawings, and all the steps in any method or processdisclosed, may be combined in any combination, except combinations whereat least some of such features and/or steps are mutually exclusive. Eachfeature disclosed in the specification, including the claims, abstract,and drawings, can be replaced by alternative features serving the same,equivalent, or similar purpose, unless expressly stated otherwise.

It will be appreciated that variants of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be combined intomany other different systems or applications. Various presentlyunforeseen or unanticipated alternatives, modifications, variations, orimprovements therein may be subsequently made by those skilled in theart which are also intended to be encompassed by the following claims.

What is claimed is:
 1. An apparatus, comprising: a first belt having anexternal surface; a second belt having an external surface positionedwith the external surface opposite to the external surface of the firstbelt, with a region in which the first belt and the second belt come incontact; a first set of guide devices arranged inside the first belt; asecond set of guide devices inside the second belt; a first materialdispenser positioned to allow a first material to be dispensed on theexternal surface at least one of the first and second belts; a secondmaterial dispenser positioned to allow a second material to be dispensedon the external surface at least one of the first and second belts; anda power source to cause at least one of the guide devices in at leastone of the first set and the second set of guide devices to cause atleast one of the first and second belts to move to cause the externalsurfaces of the first and second belts contact and then diverge awayfrom each other so that at least one of the first material and thesecond material forms filaments that break up as the belts continue todiverge.
 2. The apparatus as claimed in claim 1, further comprising acontroller connected to at least one guide device, the first materialdispenser and the second material dispenser.
 3. The apparatus as claimedin claim 1, wherein the first set of guide devices is arranged linearlywithin the first belt and the second set of rollers is arranged linearlywithin the second belt in parallel with the first set of rollers.
 4. Theapparatus as claimed in claim 1, wherein the first set of guide devicesand the second set of guide devices are offset from each other.
 5. Theapparatus as claimed in claim 1, wherein the first set of guide devicescomprises two, three or four rollers and the second set of guide deviceshas a same number of rollers as the first set of rollers.
 6. Theapparatus as claimed in claim 1, wherein the first belt and the secondbelt comprise timing belts.
 7. The apparatus as claimed in claim 1,wherein the first belt and the second belt have different textures, withone belt having a rougher texture than the other.
 8. The apparatus asclaimed in claim 1, wherein at least one of the first belt and thesecond belt is adjustable as to the length of the region of contact. 9.The apparatus as claimed in claim 1, wherein at least one of theexternal surface of the first belt and the external surface of thesecond belt has a texture.
 10. The apparatus as claimed in claim 1,wherein the first set of guide devices and the second set of guidedevices are positioned such that when the first and second belts move,alternating regions of high and low pressure form.
 11. A method ofgenerating a spray of reactive materials, comprising: dispensing a firstmaterial onto at least one of a first belt and a second belt, the firstbelt and the second belt arranged on a first set of guide devices and asecond set of guide devices; dispensing a second material onto at leastone of the first belt and the second belt; mixing the first material andthe second material by moving the first belt and the second belt througha region in which the first belt and the second belt come in contactwith each other to form a mixture; and causing the first belt and thesecond belt to diverge from each other forming filaments that break intoa spray of droplets.
 12. The method as claimed in claim 11, whereindispensing the first material comprises dispensing a cross-linkablematerial.
 13. The method as claimed in claim 12, wherein thecross-linkable material comprises a material containing one or more ofepoxy resin, silicone resin, or cross-linkable polymers.
 14. The methodas claimed in claim 11, wherein dispensing the second material comprisesdispensing a cross-linking agent.
 15. The method as claimed in claim 14,wherein the cross-linking agent comprises one of an epoxy hardener, asilicone hardener, polymer cross-linkers, and boric acid.
 16. The methodas claimed in claim 11, wherein mixing the first material and the secondmaterial comprises adjusting a distance of the region to control a levelof mixing.
 17. The method as claimed in claim 11, wherein mixing thefirst material and the second material comprises controlling a speed ofat least one of the first belt and the second belt to adjust a time thefirst belt and second belt are in contact.
 18. The method as claimed inclaim 11, wherein mixing the first material and the second materialcomprises moving the first belt and the second belt with the first setof guide devices and the second set of guide devices with the guidedevices position to form alternating regions of high pressure and lowpressure relative to each other.
 19. The method as claimed in claim 11,further comprising setting the first belt and the second belt todifferent voltages, wherein the first material and the second materialhave different dielectric constants.
 20. The method as claimed in claim11, wherein the moving of the first belt is at a different speed thanthe moving of the second belt.